In a traditional paper manufacturing process, a paper web once formed is directed in peripheral contact about one or more heated rotating drums to effectively dry the paper web. A dryer drum of this conventional type basically includes a hollow cylindrical shell substantially enclosed by opposite end heads each of which includes a central trunnion or other appropriate journal coaxial with the shell for rotatably mounting it. The cylindrical shell usually has a smooth outer peripheral surface for carrying the paper web, with the drum being interiorly steam heated to transfer drying heat through the shell to the traveling paper web. Conventionally, an axial conduit system is arranged centrally through one of the trunnions to continuously supply steam to the interior of the dryer drum while simultaneously withdrawing therefrom the water of condensation naturally resulting from the drying process.
As will be understood, the efficiency and rapidity of the web drying process is dependent directly upon the amount of heat transferred by the cylindrical shell from the drum interior to the traveling paper web. In turn, the degree of heat transfer from the steam contained within the interior of the dryer drum is dependent to a large extent upon the efficient withdrawal of the water of condensation from the drum interior. As concern has grown in recent years for greater efficiency and economy in papermaking operations, the speed of operation of papermaking machines and, in turn, of their associated dryer drums, has been significantly increased. As a result, the need for efficient condensate removal has become even more important. Particularly, in the high speed operation of dryer drums, a tendency exists for the water of condensation to form under the effect of centrifugal force as a thin sheet or film substantially entirely about the interior periphery of the cylindrical shell, this so-called "rimming" of the condensate serving to significantly inhibit the complete transfer of steam heat to the traveling paper web.
One ongoing and yet unsolved problem in the design of dryer drums resides in the accommodation for easy installation of a journal-supported conduit system of the aforementioned type. While the location of steam admission to the interior of the dryer drum is not critical to achieve sufficient heating of the drum, it is very important that the conduit arrangement for withdrawing the water of condensation have a pick-up end disposed as closely as possible to the interior peripheral wall of the cylindrical shell of the drum in order to efficiently remove condensate with minimal "rimming" about the shell interior. Over the years, two basic types of suction arrangements, commonly referred to as "siphons," have evolved. In so-called "stationary" siphons, a siphon tube assembly extends axially through the end trunnion of the dryer drum to the interior thereof and then angularly downwardly to a close spacing with the interior wall surface of the peripheral shell at its lowermost point, in which disposition the siphon tube assembly remains stationary during operation of the dryer drum to withdraw condensing water which collects under the force of gravity in the bottom of the drum over the course of its operation. In so-called "rotating" siphons, a siphon tube assembly similarly extends axially through the end journal of the dryer drum and angularly therefrom within the drum interior, the siphon tube assembly being fixed to the trunnion of the dryer drum with the interior end of the siphon tube assembly being fixed to the interior wall surface of the cylindrical shell of the drum for unitary rotation therewith during its operation.
Stationary siphons provide effective condensate removal in dryer drums operating at relatively low speeds. However, the interior suction end of a stationary siphon tube assembly must remain at a sufficient spacing from the interior wall of the cylindrical shell of the drum in order to avoid wearing contact therewith, whereby such siphons are essentially ineffective in high speed dryer drums for preventing undesired "rimming" of the water of condensation about the cylindrical shell of the drum. Rotating siphons provide considerably more effective condensate removal since a closer spacing may be utilized between the interior end of the siphon tube assembly and the cylindrical shell, but such siphons are more difficult and time consuming to install in a dryer drum because of the need to affix the interior end of the siphon tube assembly to the cylindrical shell.
For both stationary and rotating-type siphon tube assemblies, installation in a dryer drum is normally performed by assembling the components of the siphon within the drum interior through removable "handholes" or "manholes" provided in the end head of the drum. As will be recognized, this process is tedious and time consuming, particularly in that it requires that the dryer drum be cooled to a suitable temperature permitting workmen to operate within the drum interior. Various forms of siphon tube assemblies having some form of pivoting intermediate joint have been proposed to facilitate insertion of the tube assembly in a generally linear disposition through the axial trunnion of a dryer drum with subsequent pivoting of the tube assembly into an operative siphoning disposition once the pivot joint is positioned within the drum interior. Representative examples of such siphon tube assemblies are disclosed in U.S. Pat. Nos. 2,299,530; 2,617,205; 2,875,527; and 2,978,815. Pivoted siphon tube assemblies of this type advantageously simplify the installation process and are readily adapted for use in dryer drums having no handholes or manholes. However, while such siphon tube assemblies provide effective operating results when used as stationary siphons, the forms of such siphons designed for rotating-type uses have generally been found to be unacceptable for failure to provide an adequately rigid engagement of the interior suction end of the siphon tube assembly with the interior peripheral wall of the dryer drum, which may result in either or both ineffective condensate removal and possibly damaging wear to the interior of the cylindrical shell.
It is accordingly an object of the present invention to provide an articulable siphon tube assembly easily adapted for use in paper drying drums for selective articulation for insertion into and removal from the drum through its axial journal and for siphoning disposition within the drum at a peripheral drying wall thereof, all without requiring the use of any handholes or manholes in the drum. A more specific object of the present invention is the provision of an articulable siphon tube assembly particularly adapted for selective articulation within the dryer drum into rigid braced siphoning engagement with the peripheral drying wall of the drum for operation as a rotary-type siphon, while also being adapted for use in stationary-type siphon embodiments.